Tyson Gay thrilled the crowd at the London Grand Prix tonight, storming to victory in 9.78sec, the fastest time in the world this year, just seven days after beating the world record holder, Usain Bolt, in Stockholm. The American blew the rest of the field away, exploding out of the blocks and crossing the line in the second fastest 100m time ever recorded in Britain.

"I feel good," the 27-year-old said in his usual understated manner. "I wasn't expecting to go that fast in these conditions but I knew I was in good shape. I was hobbling a bit at the end – my groin is a little sore – but I'm sure it's OK."

Difficult conditions – heavy rain and cool temperatures – made it unlikely that the field would produce a fast time but Gay impressed despite the obstacles. Such a performance suggests he may yet be able to mount a legitimate challenge to the sprint crown that has, since 2008 and Bolt's emergence as a record breaker, eluded him.

"I wasn't necessarily sending a message to Asafa [Powell] and Usain," Gay said. "I was just running my own race. I think there is more to come. It is great to be on top of the world, that is important to me. This is not the best shape I have ever been in because I am still dealing with a few little injuries. My coach said I can run 9.7sec in any conditions, and I think I showed that tonight."

Neither Bolt or Powell were on the track to contest Gay's performance – both Jamaicans were missing through injury, although Bolt had already ruled out running in London because of tax issues – but if Gay can run that fast on a wet track with a strained groin he is looking like a serious contender. Rubbing his groin after the race, the second fastest man in history said he had caused the problem during the heats. "I tweaked it in the prelim [heats] but I think it will be OK. I've just got one more 100m left in Brussels and then I'll get my groin looked at."

Gay's performance was a welcome tonic to a disappointing show by the British European medal winners who, after sparkling in Barcelona two weeks ago, came back down to earth with a bump tonight, unable to clinch a single victory for the host nation.

World, European and Commonwealth champion Phillips Idowu summed up the evening when he could manage no better than 16.54m in the triple jump – a full 1.27m down on his gold medal winning performance in the European Championships. He finished sixth overall, with Christian Olsson of Sweden winning.

"I was just tired," the 31-year-old said. "Running was good but I just could not get my phases together. I would have liked to have put in a good performance in front of the home crowd."

Mo Farah, the 5,000m and 10,000m European champion, fared better, finishing second in the 3,000m behind America's Bernard Lagat. "I'm a bit disappointed to finish second but Lagat is an amazing athlete," said the 27-year-old, who perched on the shoulder of his team-mate, the European 10,000m silver medallist Chris Thompson, who finished sixth, before kicking to keep in touch with Lagat.

The European 400m hurdles champion Dai Greene was under par as the Diamond League event leader, Bershawn Jackson, stole victory in 48.12sec, with the Welshman some way behind in third place with a time of 49.09sec.

"It was difficult," the 24-year-old admitted. "Bershawn's the best in the world at the moment. I found it very difficult to raise my game after the high of Barcelona. I'm pleased to have put on a decent display though, in front of the home crowd, and top three is not so bad.

"I was rusty all the way round, you could see I've not done that much training in the last week. I wasn't million miles away from him, though. On my day I can be up there, a bit closer." Greene's training partner, Rhys Williams, a European silver medallist, finished fifth.

The European 800m silver medallist, Michael Rimmer, finished in eighth place, while the world silver medallist Lisa Dobriskey finished third in the 1500m. European silver sprint medallists Mark Lewis-Francis and Christian Malcolm failed to make the 100m final.